Cryptographic telegraph system



Aug. 13, 1946. J. w. DEHN CRYBTOGRAPHIC TELEGRAPH SYSTEM 7 Sheets-Sheet1 Filed oct. 12, 1942 /N VEN TOR J. W DE HN B59 9 A T'TORNE Y J. Aw.DEHN CRYPTOGRAPHIG TELEGRAPH SYSTEMv Aug. 13, 1946..

7 Sheets-Sheet 2 yFiled Oct. 12. 1942 /NVENTOR BYJ. W DEHN Cf? ATTO NEVJ. w. DEHN 2,405,570

Filedpct. 12, 1942 7' sheets-sheet s /NVENroR J. W DE HN Aug. 13, 1946.

J. w. DEHN CRYPTOGRAPHIC TELEGRAPH SYSTEM ,Filed 061'.. 12, 1942 7Sheets-Sheet 4 Hin /NVENTOR BYJ. W. DEH/V 0862.

Afro Ev J.`W. DEHN CRYPTOGRAPHIC TELEGRAPH SYSTEM 7 Sheets-Sheet 6 FiledOct. 12, 1942 ATOR E Y Filed oct. 12, 1942 -7 sheets-sheet 7 /Nl/ENTORJ. I4. DE HN 5v ATTO@ EY Patented Aug. 13, 1946 UNITED STATES PATENTOFFICE Bell Telephone Laboratories,

Incorporated, n

New York, N. Y., a corporation of New York Application October 12, 1942,Serial No. 461,731

34 Claims.

This invenftion relates to cryptographic telegraph systems and methodsand particularly to apparatus for generating cipher codes to be used inciphering text codes to be transmitted and in deciphering received codesto derive message text codes therefrom.

An object of fthe invention is to generate a random sequence of codesfor ciphering and deciphering transmitted and received code signals.

Another object of the invention is to determine the character of eachimpulse of a cipher code combination in accordance with the operation ofa plurality of selectively operable instrumentalities.

Another object of the invention is to control the operation of theselectively operable instrumentalities from multiple bank switchingdevices.

Another object of the invention is to control the operation of theswitching devices from certain of the selectively operableinstrumentalities.

Another object of the invention is to provide other switching devicesfor variously rearranging the operative relation between said certainselectively operable instrumentalities and the switching deviceoperating means.

Another object of the invention is to control the operation of at leastone of said other switching devices according to a predeterminedch'aracteristic of certain ones of the message text codes.

Another object of the invention is to provide means for quickly andeasily rearranging the selective control of the selectively operableinstrumentalities by their respective switching devices.

Another object of the invention is to provide means for adjusting theswitching devices to any desired position to serve as starting points.

Another object of the invention '1s to provide a relay distributor fortiming the generation of ciphered and deciph'ered signals.

The invention features a multiple contact jack or socket associated withthe contacts of each bank of the multiple bank switching devices indifferent connective arrangements from each other bank and multiplecontact jack or socket, and a plurality of multiple prong plugs havingdifferent combinations of prongs interconnected, any such plug beingusable in any one of the jacks.

The invention also features a plurality of jacks and patching cordswhich' in cooperation with selectively operable keys establish variablestarting points for the switching devices.

In accordance with the preferred embodiment of the invention, an inputrelay receives plain 55 text signals to be ciphered and transmitted oralternately receives ciphered signals to be deciphered and impressedupona receiving printer.

An output relay generates the ciphered signals to be transmitted oralternatively generates the deciphered signals to be recorded. Th'eoperating circuit of the output relay, which is polar, is completed fromthe marking or spacing contacts of the input relay, which have batteryconnections of opposite polarity, over either of two paths and throughthe segments of a transmitting distributor or through' counting anddistributing relays of a relay distributor. The operation of the outputrelay to its marking or spacing position will be dependent upon which ofthe .two paths is completed to eiect the energization of the relay, thepaths entering the operating winding from opposite sides of the relay,and which of the two contacts the armature of the input relay engages atthe time that the path is completed.

The completion of one or the other of the two paths is determined by aplurality of setsof cipher coding relays, there being a set for eachselecting impulse of a permutation code signal combination. Thearmatures of the cipher coding relays control various chain circuits forcompleting connections' from either of the output relayoperating pathconductors to the segments of the distributor or to the counting anddistributing relays. Each of the cipher coding relays is controlled froma switch bank which has approximately one half of its contacts connectedto the associated relay through a multiple contact jack or socket andassociated plug. There is a full set of connections from each switchbank to its jack and the selective extension of paths from about onehalf of the switch bank contacts to the relay is determined by theelectrical interconnection of about h'alf ofthe prongs of the plugs.Plugs having various arrangements of interconnection of their prongs areemployed so that the selective control of the coding relay from its bankmay be varied by the substitution of plugs.

The switch banks which control the cipher coding relays comprisemultiple bank stepping switches so arranged that each switch has onecontact bank assigned to control a relay in each of the sets of ciphercoding relays, from which it follows that each of the relays in a set iscontrolled from a diierent stepping switch.

In addition to determining which of the two paths will be completed foroperation of the output relay, certain of the cipher coding relays alsoselectively provide ground connections for a number of conductors equalto the number of f 9,405,976 j j 3 stepping switches which control thecipher coding relays. These conductors extend to the contact brushesassociated with an equal number of contact banks of another steppingswitch. The conductive paths to the contact brushes of thelast-mentioned stepping switch are completed through a mixing jack withwhich several different plugs may be employed for varying theconnections between the conductors and the brushes. The contacts of thebanks of the lastmentioned stepping switch are connected in variouscombinations to five conductors which extend to the brushes of stillanotherstepping switch. The contacts of the banks of this steppingswitch are connected in different combinations to five conductors whichextend to the normally released armatures of a timing relay. From thefront contacts of the timing relayn `conductors extend through anothermixing jack and plug combination tothe lstepping magnets of the steppingswitches which control the cipher coding relays, so'` that the operationof the stepping magnets forV theV Ystepping Vswitches which control theciphercoding relays will depend upon the selective application of groundto the conductors extending to the brushes of the first transposingstepping switch and the manner in which the twotranspcsing steppingswitches transpose the conductive paths to the several stepping magnets.

One of the transposing steppingv switches is advanced one step for eachsignal combination transmitted or received. The advancement of theothertransposing stepping switchv is dependentupon two factors. One is theVpreparation of a ground connection for the stepping magnet of the secondtransposing stepping switch through a chain circuit controlled bycertainof the cipher coding relays. The'other condition is the appearance .ofmarking as the'nature of aparticular one of the impulses of the plaintext codes. When these two conditions appear concurrently,

v the second transposing second switch is advanced one step.

The `appearance of the marking-condition forY a particular impulse ofthe text code signals isY detected'by a' relay Which'iscontrolleddirectly bytheinptrelay in the case of signal transmission, because theplain text codes are impressed directly upon the input relay under thosecircumstances, and is controlled in accordance with the operation of theoutput relay in the case of the received signals since the input relayis then responding to ciphered signals and the output relay operates inaccordance with the deciphered plain text signals. Y i

'Each ofv the. stepping switches which control the cipher coding relayshas one more bank of contacts than the number of sets of coding relaysand leach of the two transposing stepping relays has an extra contactbank. By means of a sys-` rupter or buzzer action. When'each steppingswitch reaches the contact to which a conductive path for energizing thesteppinggmagnet has been extended, the stepping magnet will be heldenergizedY over a path in shunt relation to the path through theinterrupter contacts whereby the 4 automatic advancement of the steppingswitch will be discontinued. When all of the switches have come to rest,the manually controlled relay may be released whereby the energizingcircuit for the stepping magnet will be interrupted and the brushes ofthe stepping'switches will be in starting positions as selected inaccordance with thefpositions of the patching cords relative to thejacks and in accordance with the particular manually operable keys whichhad been op- Y erated.

For a complete understanding of the invention reference may be had tothe following detailed description to be interpreted in the light of theaccompanying drawings wherein: i

Figs. 1 'to 6, inclusive, are diagrammatic views showing parts of acryptographic telegraph system in accordance with the present invention;

Fig. 7`is a diagrammatic view showing how Figs. 1 to 6, inclusive, areto be arranged to represent a complete telegraph station capable ofciphering and deciphering telegraph messages; and

Fig. Sis a diagrammatic view showing an alternative embodiment of theportion of the system shown in Fig. 1.

Fig. 1 is largely similar to Fig. 1 of the patent concurrently grantedon copending application, Serial No. 435,178, led March 18, 1942, by K.E.

. Fitch et al. Fig. 2 of Fitch'et al. discloses a special repeater whichcooperates with the apparatus of Fig. 1 of that application andarepeater identical withkthat shown in Fig. 2 of the copendingapplication is intended to cooperate s similarly with Fig. 1accompanying the presentY specication. For the purpose of simplifyingthe present specification and avoiding duplication of disclosure, thedrawings accompanying the present specication do not include therepeater, nor does the specification contain detailed description ofsuch repeater. In View of this the disclosure of the copendingapplication and particularly Fig. 2 and the descriptive materialpertaining thereto of the copending application is incorporated hereinby reference as part ofthe present specification. 7

Referring now to the drawings and particularlyrto Fig. 1 the apparatusVcontainedwithin the broken 1ine rectanglel II represents a combinedreceiving telegraph printer and keyboard transmitter which may be of thetype `shown in'V Patent 1,904,164, granted April 18, 1933, Vto S.;

Morton et al. The disclosure `of kthe Morton patent is incorporatedherein by reference as part of the present specification; In Fig. 1 theprinter is indicated symbolically by the selector magnet I2 and thekeyboard transmitter for transmitting start-stop permutation codesignals is represented by the transmitting contacts I3. The selectormagnet I2 is connected to the sleeve terminals of a double plug I4andthe transmitting contacts I3 are connected to the tipterminals of the-double plug I 4. The double plugld is adapted to be inserted intoeither of two pairs of jacks associated with the repeater circuit shown'in Fig, v2 of the copending application, depending upon whether it isdesired to transmit straight unciphered message text signals or cipheredsignals.

A ciphering and deciphering relay shown -in the lower right-hand portionof Fig. 1 comprising relays I6 and yI'I. Relay I6 is adapted t0 receivesignals from the repeater circuit,

' (not shown) and has one terminal of its upper or system is whichextends into the repeater circuit and the other terminal of the'operating winding is connected through resistor I9 to ground andthrough resistor 2| to the negative terminal of battery 22, theresistors I9 and 2| forming a potential divider. In the repeater,conductor I8 receives negative battery connection in the idle conditionWhich causes current to flow in the operating Winding of relay I6 in adirection to hold the armature on the marking contact, which has anegative battery connection. When the repeater receives a spacing signaleither from the local transmitting contacts I3, which generate straighttext signals, or from a remote station, a ground connection on conductorI8 is substituted for the connections as will be described later. Fromthe negative battery connection, which causes current to flow in theopposite direction through the operating winding of relay I6 and drivesits armature to spacing which has ground connection. Relay I6 has aholding or locking winding, one terminal of which is connected throughresistor 26 to ground and through resistor 21 to negative battery 23,the resistors 26 and 21 cornprising a potential divider, and the otherterminal of the holding winding of relay I6 is connected over conductor29 to the collector ring of a cipher code generating distributor 3|which will be described later.

The transmitting relay I1 has its armature connected to a conductor 32Which extends into the repeater, its marking Contact connected tonegative battery and its spacing contact connected to ground. When thearmature of relay I1 is on the marking contact a marking signal istransmitted into ythe repeater and when the armature of relay |1 movesto the spacing contact a spacing signal is transmitted into therepeater. Relay I1 is operable under the joint control of receivingrelay I6 and cipher code generating distributor 3|. When relay I6responds to a plain text code generated by transmitting contacts I3 andcauses the operation of relay I1, the signal transmitted by relay I1 isa ciphered signal and is repeated by the repeater into a line extendingto a remote station. When relay I6 responds to a ciphered code receivedfrom a remote station, the operation of relay I1 in response thereto isto decipher the code and the signal transmitted by relay I'I into therepeater is repeated to the selector magnet I2 of the receiving printer.The armature of relay I'I is also connected to one terminal of theholding or locking Winding of that relay, the other terminal of which isconnected through resistor 33 to ground and through resistor 34 tonegative battery 36. The holding winding thus may be traversed bycurrent in either direction from the marking and spacing contacts ofrelay I1 and serves to hold the armature in the position to which it isoperated by the operating winding until the operating winding, which isparamount to the holding Winding operates the armature to the oppositeposition.

The armature of input relay I6 is connected by conductor 31 to onecorner 38 off a triangular bridge network which comprises one side orarm containing resistor 39, a second side or arm containing resistor 4I,and a third side or arm containing the operating Winding of output relayI1 and resistor 42 in series therewith, From the point ofinterconnection of the operating winding of relay I1 and resistor 4|,designated as the bridge corner 43, conductor 44 extends to the stopsegment 46 and to the start segment 41 of distributor 3| and into Fig. 2where it has various point of interconnection of resistors 39 and 42,designated as bridge corner 48, conductor 43 extends into Fig. 2 and hasvarious connections in that gure. From the bridge corner 38 conductor 5Iextends to the rest segment 52 in the outer ring of distributor 3|.

The distributor 3| is somewhat similar to a tape controlled transmitterdistributor disclosed in Patent 2,055,567 granted September 29, 1936, toE. F. Watson, and the disclosure of the Watson patent is incorporatedherein by reference as part of the present specication. However, thedistributor has a considerably diierent arrangement of signal generatingsegments and there are no tape-controlled contacts, the segmentsreceiving their potentials from other sources as will be describedhereinafter.

The distributor 3| has a brush arm 53 which is carried by a rotatableshaft 54 to which rotation is imparted from motor 56 through frictionclutch 51 and gears 58. to shaft 54 and is arranged to be arrested bythe armature lever 6I of electromagnet 62 when the magnet isdeenergized. Upon the energization of magnet 62 the end of armaturelever 6| presented toward cam 59 is rocked out of. blocking relation tothe cam whereby shaft 54 is released for rotation. Brush arm 53 carriestwo electrically interconnected brushes which bridge outer and innersegmented rings.

The inner ring of the distributor is electrically continuous except fora short conductive segment 63 insulated from the main body of the ring,and the inner brush carried by brush arm 53 is in engagement with thesegment 63 when brush arm 53 is held at rest, the outer brush thenengaging rest segment 52 which subtends the same angle as the segment53. The stop segment 4E is traversed by the outer brush of arm 53 justbefore reaching rest segment 52 and the start segment 41 is traversed bythe outer brush immediately after leaving segment 52. The remainder ofthe outer ring contains five uniformly spaced short conductive segmentsWhich correspond to the five code impulses of a permutation codecombination and these segments are connected to conductors 66, 61, 68,69 and II ywhich extend into Fig. 2. The inner ring of the distributor,exclusive of the rest segment 63, has one end in registry with thebeginning of start segment 41 and the other end in registry with the endof stop segment 46 and thus is arranged to complete conductive pathsfrom the start segment, the five code segments and the stop segment overconductor 29 to the locking Winding of input relay I6.

With distributor brush 53 in the rest position the two rest segments 52and 63 are bridged by the brushes as previously stated and a circuit may-be traced from ground on the positive terminal of a battery 12 throughthe battery, resistor I3, Winding of start magnet 62, conductor 14,inner rest segment 63, brushes carried by distributor arm 53, outer restsegment 52, conductors 5| and 31, armature of input relay I6, andmarking contact of that relay to negative battery, the positive terminalof which is connected to ground. The negative battery connected to themarking Contact of relay I6 opposes the negative battery connected tostart magnet 62 so that the magnet is deenergized. When input relay I6goes to spacing in response to the 'start impulse of a signalcombination received over conductor I6 the opposing negative batteryconnection on the marking contact of relay I6 is removed from the A stopcam 59 is secured circuit of start magnet B2 and a ground connection onthe spacing contact is substituted so that the magnet becomes energizedand retracts armature lever 6I from blocking relation to start cam 59thus permitting distributor shaft 54 and brush arm 53 to be rotated.

Referring now to Figs. 2 and 3 the apparatus for setting up cipher codeswill be described. It may be stated generally that this involvesselective determination of the completion of conductive paths overconductors 44 or 49 which extend from the bridge network corners i3 ord8 and thus from the opposite ends of the winding of output relay I1, tothe five code segments of distributor 3|. In the lower portion of Fig. 3are shown the stepping magnets Sl, 82, 83, 84 and'B 'of ve steppingswitches each of which has six banks of contacts. The Contact bank-sassociated with the stepping switch operated by stepping magnet 8| aredesignated 3 IA to 8 IF, inclusive. Similarly, the banks of contactsassociated with the stepping switches controlled by the stepping magnets82 to 85, inclusive, are designated 82A to B5F, inclusive.

Associated with the stepping switch banks SIA to 8IJE are individualrelays 8 IAR to BIER. Similarly, the stepping switch banks 82A to 82Ehave relays SZAR to SEER, respectively, the switch banks 83A to 83E havethe individual relays 83AR to BSER, the banks 84A to 84E have relays MAR-to MER, and the switch banks 85A to 85E have the relays BSAR to BEER.The switch banks bearing designations A to E, inclusive, include uniformnumbers of contacts, such as 22, and the brush associated with each ofthese banks is connected to ground. The association of a relay with itsswitch bank is 'shown in full detail in the case of bank 85E land relayMER in Fig. 3. The

twenty-two contacts of 'switch bank 85E are connected to individualsingle contact'spring jack elements of a multiple jack SSEJ which has aminimum of twenty-three individual jack spring elements. Successivecontacts of lbank 85E are not connected to successive jack springelements of the multiple jack 85EJ but are scrambled or connected inpurely random fashion. The uppermost jack spring element of jack 85EJ isconnected to one terminal of relay EEER the other terminal of which isconnected to grounded vbattery. There is provided for cooperation withjack B5EJ a multiple plug 85EP having a minimum of twenty-threeindependent contact prongs. The uppermost prong is connected byconductive straps to about one half of the other twenty-two prongs,selected at random. With the plug 85E? inserted into jack 85EJ, when thebrush associated with switch bank 85E co-mes into engagement withcontacts of the bank from which conductive paths extend through springsof jack 85EJ to prongs of plug 85EP that are connected to the uppermostprong, the circuit of relay 85ER. will be completed and the relay willbe energized. With the specific arrangement of connections betweenswitch bank 'E and jack 35EJ, and with the specific strapping of prongsof plug 85E? to the uppermost prong the circuit of relay 85ER will becompleted Iwhen the stepping switch brush engages the rst, fifth, sixth,eighth, ninth, eleventh, fourteenth, twentieth, twenty-first andtwenty-second contacts of the bank,

Fragments of other multiple jack and multiple plug arrangements areindicated 85D] and DP, respectively, in Fig. 3 and in Fig. 2 inassociation with switch bank SiC by the reference numerals 8ICJ and8|CP, respectively, and in association 8 with the switch bank 83C by thereference numerals 83CJ and 83CP, respectively. Each of the twenty-vestepping switch vbanks which controls a relay has a set of connectionsfrom its twentytwo contacts to twenty-two jack springs of its multiplejack which differs from the arrangement of connections between theremaining twentyfour switch banks and their multiple jacks, and each ofthe multiple plugs of which thereis a minimum .of twenty-ve has adifferent combination of strappings from the uppermost prong to aboutone half of the remaining twenty-two prongs of the plug. Any one of theplugs may be used in any one of the jacks to establish selectivelyvariable paths for the energization of the relays. The multiple plugs,the number of which may considerably exceed twenty-ve, because a largenumber of different strapping combinations may be made, may be markedwith distinctive identifying symbols so that they may be placed inconductive association with the multiple jacks in predeterminedarrangement according to charts or other instructions.

Each of the relays controlled by the stepping switch bank has asufficient number of armatures and contacts to provide two normal pathsand two off-normal paths, the normal paths being those that areestablished through back contacts and the oir-normal paths being thosethat are established through front contacts. `In the majority cfinstances this could be accomplished by providing relays having twoarmatures each operable between a back contact and a front contact.However, in Figs. 2 and 3 the relays have been shown as being providedwith four armatures two of which cooperate only with a back contact andthe other two of which cooperate only with a front contact. In someinstances only one back contact is used and, accordingly, one of thearmatures is not used. However, in systems of this type it is desirableto use similar relays throughout where they perform similar functionseven though some of the armatures and contacts may not actually be used.The reason for this is that it may be desirable to rearrange some of thepermanent connections from time to time and if all of the relays havefull complements of armatures and contacts the rewiring may be donewithout the necessity of removing and substituting relays.

As previously stated the conductors 44 and 49 connected to the oppositeends of the winding of output relay I7 extend into Fig. 2. In branchingrelation to conductors 44 and 49 the conductors 44A and 49A extend toarmatures of relays BIAR and BSAR. VConductor 44A is connected toarmatures l and 4 of both relays, which have off-normal and normalrelation respectively to their contacts. Conductor 49A extends to thearmatures 2 and 3 of both relays 8|AR and 83AR. Of these armatures thearmature 2 has normal relation to its contact and the armature 3 hasoffnormal relation to its contact. The contacts'of the armatures l and 2of relay BIAR are connected to the armature l of relay 82AR. Thecontacts of the armatures 3 and 4 of relay HAR are connected to thearmature 2 of relay BZAR. The contacts associated with the armatures Iand 2 of relay 82AR are connected to the armature I of relay BSAR. Thecontacts associated with the armatures l and 2 of relay 83AR areconnected to the armature I of relay MAR and the two contacts associatedwith the armatures 3 and 4 of relay 83AR are connected to the armature 2of relay 84AR. The two contacts associated with the armatures I and 2 ofrelay 84AR are connected to the armature 2 of relay BEAR. The contactsassociated with the armatures I and 2 of relay 85AR are connected overconductor 66 to the No. l code segment of distributor 3|.

With relay armature and contact connections as described above, thereare two chain circuits, one comprising the armatures and contacts ofrelay 8|AR and the upper two armatures and contacts of relay 82AR andthe other comprising the armatures and contacts of relay B3AR and theupper two armatures and contacts of the relay 84AR, these two chainsleading into the upper two armatures of relay BEAR. Conductors 44A and49A enter both of these chain circuits. When relay 85AR is deenergizedthe chain circuit cornprising relays 83AR and 84AR will be effective tocontrol connections from conductors 44A and 49A to conductor 66. Withboth of the relays 83AR and 84AR energized Or both deenergized,conductor 44A will be connected t0 conductor 66. With either of theserelays energized and the other deenergized conductor 49A will beconnected to conductor 69. When relay 85AR is energized the chaincircuit controlled by relays 8|AR and 82AR will be eiective. With bothof these relays energized or both deenergized, conductor 44A will beconnected to conductor 66 and with either of these relays energized andthe other deenergized, conductor 49A will be connected to conductor 66.As the ve relays are selectively operated singly or in combinations,they cooperate in sets of three, namely, SIAR, BZAR and BEAR, or 83AR,84AR and 85AR to determine which of the two conductors 44A and 49A shallbe connected to conductor 66. The chain circuits are so arranged that itis not possible for both of the conductors 44A and 49A to be connectedto conductor 66 simultaneously.

The relays BIBR, 82BR, 83BR, 84BR. and 85BR control chain circuitsidentical with those controlled by the relays BIAR to BSAR. It is notnecessary that these two chain circuit systems be the same, as there aremany ways in which the chain circuits may be arranged, and other sets ofrelays controlled by the stepping switches control diferent arrangementsof chain circuits, as will be described later. The conductors enteringthe two chain circuits at the armatures of relays `BIBR and 83BR havebeen designated by the reference numerals 44B and 49B. The conductors44B and 49B do not connect directly to conductors 44 and 49,respectively, as do the conductors 44A and 49A, respectively, butconnect instead to the outer left-hand armature and to the right-handarmature, respectively, of a relay 9I. The back contact of the outerleft-hand armature of relay 9| is connected through the second winding,counting from the top, of a relay 92 to conductor 44. Similarly, theback contact of the right-hand armature of relay 9| is connected throughthe third winding of relay 92 to conductor 49. The front contact of theouter left-hand armature of relay 9| is connected directly to conductor44 and the front contact of the right-hand armature of relay 9| isconnected directly to conductor 49. Thus when relay 9| is deenergizedconductors 44 and 44B are interconnected through a winding f relay 92and conductors 49 and 49B are interconnected through another winding ofrelay 92 whereas when relay 9| is energized conductors 44 and 44B areinterconnected directly and conductors 49 and 49B are interconnecteddirectly, the two windings of relay 92 being open.

. Conductor 61B extending from the contacts of the armatures l and 2 ofrelay SEBR extends to the back contact of the inner left-hand armatureof relay 9| and to one terminal of the uppermost winding of relay 92,the other terminal of which is connected to the front contact associatedwith the same armature. The armature is connected to conductor 61 whichextends to the No. 2 code segment of distributor 3|. When relay 9| isdeenergized, conductors 61 and 91B are interconnected directly and thecircuit of the uppermost winding of relay 92 is open. When relay 9| isenergized, conductors B'I and 61B are interconnected through theuppermost winding of relay 92.

The operation of relay 9| is controlled by contacts I93` shown inFig.` 1. Contacts 99 are normally open but are closed'by the operationof a locking bail arm 94 which is rocked in counterclockwise directionby a spring 96 under the control of a cam 91 associated with the camassemf bly which controls the operation of transmitting contact |3. Caml9'! is shown in the rest position and is rotated one revolution foreach code Combination generated by transmitting contacts |3. Thisfeature is more fully disclosed in Patent 2,018,368 granted October 22,1935, to R. A. Lake and particularly` in Fig. 5 'oi' that patent. Thedisclosure of the Lake patent is incorporated herein by reference aspart of the present speciiication. One of the contacts 93 is connectedto ground and from the other contact a conductor 98 extends into therepeater circuit (not shown) for effecting a control fully disclosed inthe copending application. A branching conductor 99 extends fromconductor 98 toone terminal of relay 9| (Fig. 2) the other terminal ofwhich is connected to grounded battery of the same polarity as thebattery connected to conductor 98 in the repeater circuit, so that whencontacts 93 are closed, relay 9| will be energized and when contacts 93are open no energizing circuit for relay 9| will be completed throughconductor 99 into the repeater circuit. From the foregoing it will beapparent that relay 9| will be energized only during the transmission ofsignals generated by transmitting contacts lf3. When signals are beingreceived from a distant station over conductor I9 the local transmitterwill not be operated, contacts 93 will remain open and relay 9| willremain released.

Before proceeding with the description of further features and elementsof the apparatus, the operation of the apparatus heretofore described inciphering signals to vbe transmitted to a distant station and indeciphering signals received from a distant station, will be described.The ciphering of a signal to be transmitted will iirst be considered.Upon the operation of transmitting contacts I3 to transmit a signal, thefirst impulse is the start signal which is of spacing nature and thiscauses the relay 6 to go to spacing, thus completing the energizingcircuit for start magnet 62 over a circuit previously traced. The startmagnet permits brush arm 53 to be driven and the brushes iirst encounterstart segment 41. This segment is connected to conductor `44 so thatconductor 44 becomes connected to conductor 29 through the brushes ofthe distributor while the outer brush is traversing the start segment41. Conductor 49 has no direct connection to any segment of thedistributor 3| but extends directly to the cipher coding relay system inFigs. 2 and 3, the return leads of which are to the code segments of thedistributor, so

that no circuits can .be completed over conductor 49 while the brushesare .traversing the start segment. Accordingly, a circuit is traced fromground .on the spacing contactof relay `I 6 through .the armature of therelay .and conductor 3.1 to the bridge corner l38. At this point thecond-uctive .path divides, part of the current flowing over resistor 4Ito the bridge corner E3 and the .remainder flowing through resistors 39,4'2 and operating winding of .relay I1 from right to left to the bridgecorner 4.3. r.he path reunites at the bridge corner 4'3 and .continuesover conductor 44 tothe start segment 4 1 then Vto the inner ring ofYthe distributor, conductor 29 locking Winding of relay I6 and theresistor 21 through battery 28.to ground. Output relay I] is polar andwith ground .on the armature of relay I6 and the circuit .of theoperating Winding of relay I1 extended -over conductor .44, currentflows through the .operating Winding of relay I1 in the direction todrive the armature of that relay to spacing. The current through thelocking winding of relay IS is Vin the direction to 4hold relay 6 .inthespacing condition even though the start impulse of spacing naturereceived over conductor l8should cease and a marking impulse should lbesubstituted before the .brushes have left .start segment 41.. From thisit vfollows that .the locking windingof relay 'I 6 is paramount to theoper.. ating Winding. With relay condition a spacing impulse istransmitted over conductor 32 to the repeaterJ wherein it is repeated tothe Aline extending to the distant station, and current is .suppliedfrom the spacing contact of relay I1 through .the locking winding ofthat relay in the direction to hold the relay in the spacing condition.As soon as the brushes leave vthe .start .segment y4'! the circuitthrough the operating winding of output relay I1 and through 'theflocking Winding of input 'relay 16 is interrupted but the circuitthrough the locking winding of .relay I1 remains. Relay I 6 is noW free'to be operated in response to the first code impulse of the signal butthe locking Winding of relay I1 assures .that the start signal shallendure until a circuit through the operating Winding of relay l1 isagain completed, which cannot occur until the brushes reach the No. 1code segment ofthe distributor. The .operating `Winding of relay I1 isparamount to .the locking Winding and can move the armature of the relayWhenever .the operating winding becomes energized, although the lockingWinding is seeking to hold the armature in Vthe position to yWhich ithad last been moved.

Assume that the first code impulse of the signal generated by contactsI3 'is of marking nature, as a result vof which a marking signal will bereceived b y .relay I6 over conductor I8 and the armature will .berestored to the marking position. Assume alsothat the relays SIAR toBEAR are lenergized in such combination that 'a conductive path will beextended over conductors M and 44A to conductor 66. For this .conditionthere 'are four possibilities. vIf relay 85AR is deenergized theconnection will be established with both of the relays BSAR and .84ARalso deenergized or with both of 'the relays BSARv and MAR energized,the relays '8,IAR and 82AR having no effeet. If, on the kother hand therelay SSA'R is energized, the connection will be established with bothof the 'relays BIAR and 82AR alsofenergized or With the relays 8IAR 4andBEAR both deenergized, the relays .BBAR and MAR having no effect. The.circuit is traced from ground through I1 in the spacing l the batteryon the-,marking .contact of relay IB through the armature of that relay,conductor .31 through the branching paths of the bridge net- Workincluding the operating winding of relay I1 then through conductors 44and 44A, armatures and contacts of relays BIAR to BSAR, conductor 6B,the N o. 1 contact of distributor 3|, the brushes and inner ring of thatdistributor, conductor 29, locking winding of relay I S'and resistor Zyto ground. Except for the .addition of conductor 44A, contacts and.armatures `of relays BIAR to 8 5AR and conductor B6, this ,is .the same,path that was traced inconnection with the transmission of -,the startsignal. However., `the polarities have been reversed because thearmature A of relay l' now receives battery .connection instead ofground connection. Thereversal of polarity on the bridge ,network andthrough .the operating winding -of .relay l1 causes the armature of thatrelay to ,be moved to its markingcontact to effect the transmission ojfa marking signal overcomductor 32 and to com-plete a circuit .from 4themarking contact through the locking winding of relay I1 to hold thearmature on themarking contact. If the first impulse of the code.combination had been spacing the polarity applied to the bridge circuitnetwork would have been the same .as that applied in response to .the,start signal and with the circuit completed to conductor .29 overconductor M the armature of relay I1 would have remained on the spacingcontact,

Assume now that the No. 1 impulse of the code combinationis marking,Which Was the condition originally assumed, but that the relays BIAR. toBSAR are energized in such combination that they complete vaconductivepath to conductor 6 6 over conductor 49A from conductor 49.There are four conditions of the relays under which this can occur. Ifrelay 85AR is deenergized the connection will be made if either Iof therelays BSAR or 84AR is energized and the other is .deenergized therelays lARand BZAR having no effect. On the other hand, if the relayBSAR is energized, the circuit will be completed if either of the relaysSIAR or 82AR is energized and the other is deenergized, the relays 83ARand BIIAR having no effect. The circuit is traced from .ground throughthe battery on 'the lmarking contact of relay IS through the armatureandconductor 31 tothe bridge'corner 38. The .current now .divides in adifferent manner, one path being traced through resistor 39 ,to bridgecorner 48 and the l other being traced through resistor 4I, operatingWinding of relay I1 from leftto right and resistor 42 t'o'bridge corner45. From this `point the cirarmatures and contacts of relays MARIO 85AR,conductor 66, the No. 1 code segment, brushes and inner ring ofdistributor 3|, conductor 29 locking winding of relay I6 and resistor 26to ground. With the circuit completed from bridge corner v118 instead ofbridge corner 43 the current through the operating Winding of relay I1is in the `reverse of the direction in which it ilowed when with thearmature of relay I6 on .the marking contact the circuit was completedthrough conductor `MLso that the armature .of relay I1 .is driven to thespacing contact to transmit a spacing signal over conductor 32 and thecurrent through the locking winding-of relay I 1 holds the armaturev onthe spacing contact. There has been no reversal of the direction ofcurrent through the locking Winding of .relay |76 so that its .armatureremains on the marking con-tact. If instead of being of marking naturethe first vcode impulse generated by transmitting contacts I3 had beenof spacing nature, with the path to the locking winding of relay I6extended over conductor' 49 as just described there would have been areversal of the polarity on the operating winding of relay Il which overthe same conductive path would have caused the armature of the relay toassume the marking position.

By Way of recapitulation there are four possible conditions of signaltransmission. When relay I6 responds to a spacing signal and the circuitis completed over conductor 44 a spacing signal will be transmitted overconductor 32. When relay I6 responds to a marking signal and the circuitis completed over conductor 49, a spacing signal will be transmittedover conductor 32. When relay IB responds to'a's'p'acing signal andthe'c'ircuit is completed over conductor 49 relay I1 will be operated tomarking to cause the transmission of a marking signal over conductor 32.When relay I5 responds to a marking signal and the circuit is extendedover conductor 44, relay I1 will be operated to marking and a markingsignal will be transmitted over conductor 32. The further summarizingstatement may be made that relay Il. operates in correspondence withrelay I6 when the circuit is completed over conductor 44, and operatesin reverse relation to relay I6 when the circuit is completed overconductor 49.

After the brushes have traversed the ve code segments and the cipheredimpulses have been transmitted, the brushes traverse the stop segment4t. At this time the relay IG receives the stop pulse, of markingnature, generated by contacts I3. 'I'he circuit is completed from themarking contact of relay IE through the bridge network including theoperating winding of relay I'I, over conductor 44, stop segment 4S,inner ring of the distributor, and conductor 29 to the locking Windingof relay IS. This corresponds to the fourth condition recited in thepreceding paragraph of recapitulation and relay I'I will be operated tothe marking condition to transmit a marking signal, which is the truestop impulse.

It is to be noted that the cipher coding relays SIAR to 85ER in Figs. 2and 3 have no effect upon the transmission of the start and stopsignals. The circuit through the operating winding of relay Il iscompleted through conductor 44 in both cases, but relay IE is spacingfor the start signal and marking for the stop signal, and relay I'I iscorrespondingly driven spacing for the start signal and marking for thestop signal.

After the brushes leave the stop segment they encounter the restsegments and are arrested, since the start magnet 62 was released whenthe brushes left the rest segment and presumably the relay I6 will stillbe responding to the stop signal when the brushes reach the restsegments, so that the start magnet will remain released. When the relayIB responds to the start signal of the next code combination, magnet 62will again be energized and Will release the shaft 54 for another cycleof rotation.

There will now be described the operation of deciphering received codecombinations. The code combinations are transmitted from a distantstation having ciphering apparatus of the same type as that disclosed inthe drawings accompanying the present specication and it is acharacteristic of the system that when ciphered messages are beingtransmitted identical arrangements of connections between the ciphercoding relays and the stepping switch banks are established at bothstations and the brushes of the stepping switches are adjusted to thesame starting points and are advanced together by local controlindividual to the stations, so that the cipher coding relays at thereceiving station establish the same connections from the conductors 44and 49 to the distributor code segments as are established at thetransmitting station. It has been shown that the cipher coding relayshave no effect upon the output relay I'I when the input relay I 6responds to the start signal of spacing nature and therefore thattheoutput relay follows the input relay to spacing condition. When thestart signal of spacing nature is received from the distant station itis repeated by the repeater to the input relay I E which completes acircuit over conductor litandthe start segment of the receivingdistributor, which was released for rotation when the start signal wasreceived, to the locking winding of input relay I6 and the output relayII goes to spacing.

The first message code impulse was previously assumed to be of markingnature with the cipher code circuit established over conductor 44 and itwas found that the output relay transmitted a marking signal.Accordingly, the input relay of a receiving station would go to markingcondition and would complete a circuit over conductor 44 identical withthat which was described when the first impulse of text code was assumedto be marking. The polarity on this circuit is such that the outputrelay I1 is operated to the marking condition and impresses a markingsignal on conductor 32 which is repeated to the selector magnet I2. Inthis way the original text marking signal, which was treated in such away by the cipher code relays that it was transmitted unchanged as amarking signal, is received and similarly treated through an identicalarrangement of the cipher code relays and is repeated unchanged as amarking signal which is used to control the receiving printer.Corresponding deciphering operations occur with reference to the otherthree possible conditions. Thus with a text code impulse of spacingnature controlling output relay I'I over conductor 44 and causing therelay to transmit a spacing signal, the received spacing signal,controlling relay I'I over conductor 44 causes the output relay Il togenerate a spacing signal which is repeated to the printer magnet I2. Atext code marking impulse, controlling the output relay I1 overconductor 49 to cause the relay to transmit a spacing signal, isreceived in cipher as a spacing signal which, controlling output relayII over conductor 49 causes the relay to generate a marking signal whichis repeated to the selector magnet I2. Finally a text code signal ofspacing nature controlling the output relay I 'I over conductor 49 tocause the relay to transmit a marking signal is received as a markingsignal by the input relay I6 and, controlling output relay II overconductor 49, causes the relay to generate a spacing signal which isrepeated to the selector magnet I2. From this it will be apparent thatthe deciphering of received signals in order to derive the plain textcodes therefrom is accomplished by ciphering received codes under thesame conditions that were employed at the transmitting station toconvert the text code signals into ciphered signals.

Reference has been made previously to the fact that the chain circuitarrangements of armatures and contacts of the cipher coding relays maydiffer from the arrangement of the contacts and armatures of relays BIARtoV B5AR and of connected to the brushes associated with contact banks|3|A to |3|E, respectively, of a stepping switch which is operable bystepping magnet |3| and which has a sixth contact bank designated |3|F.The contacts of the five stepping switch banks |3|A to |3|E areconnected in a manner similar to the contacts of stepping switch banks|215A to |25E, but in different combinations, to ve conductors |36, |31,|38, |39 and |40 which extend to the inner right-hand armature and tothe four left-hand armatures of a relay |4l. These five armaturescooperate with front contacts from which ve conductors |46, |41, |48,|49 and |50 extend to the lowermost group of ve single circuit jackspring elements of multiple jack H8. A multiple plug |5| has ten prongswhich enter the ten lower jack elements of multiple jack I8 and each ofthe lower ve prongs of plug |5| is connected to one of the upper fiveprongs of that plug. Several plugs having diiTerent connections asbetween the lower five and the upper ve prongs may be employed forvarying the connections between conductors |46 to |50 and the thirdgroup of ve jack elements of multiple jack I8, counting the groups fromthe top. From these five jack elements conductors |6|, |62, |63, |64 and|65 extend into Fig. 3 and connect individually to one terminal of eachof the stepping magnets 8| to 85, the other terminal of which isconnected to battery. It will be apparent that as conductors |33, |04,|09, |4 and ||1 receive ground connection selectively under the controlof certain of the relays controlled by the stepping switch banks inFigs. 2 and 3, such ground connections will be extended to certain onesof the conductors 2|, |22, |23, |24 and |25 depending upon thearrangement of interconnection of the prongs of plug H9, then to certainones of the conductors |26, |21, |28, |29 and |30, depending upon theposition of the brushes associated with stepping switch banks I25A to|25E, then to certain ones of the conductors |36, |31, |38, |39 and |40,depending upon the position of the brushes associated with the steppingswitch banks |3|A to |3|E, through the inner right-hand and the fourleft-hand armatures of relay |4| when that relay is energized, throughconductors |46, |41, |48, |49 and |50 to certain ones of the conductors|6|, |62, |63, |64 and |65, depending upon the arrangement ofinterconnection of the prongs of multiple plug |5l, through the windingsof certain ones of the stepping magnets 8| to 85 (Fig. 3)1, to batteryto cause the energization of the stepping magnets. The energization ofthe stepping magnets will occur upon the energization of relay |4|, andthe release of the stepping magnets upon the release of relay 4| willcause the stepping switch brushes controlled thereby to advance onestep, since these stepping switches are of the type which advance thebrushes on the back stroke or release of the stepping magnet.

One terminal of relay |41 is connected to grounded battery and the otherterminal is connected to conductor |42 extending into Fig. 1 and thereconnected to one contact of a normally open contact pair |43, the otherContact of which is connected to ground. Contacts |43 are operable by acam |44 carried by the driving shaft 54 of distributor 3| and the cam|44 is arranged to close contacts 43 after the brushes have traversedthe start segment 41 and t0 permit the con tacts |43 to open just beforethe brushes encounter the rstop segment 46. From this it will beapparent that the stepping magnet in Fig. 3 will be energized prior tothe transmission of the first code impulse of a code combination andwill be released to effect the advancement of the stepping switchbrushes after the transmission of the last code impulse of a codecombination has been initiated, so that the cipher coding relays willnot be disturbed during the ciphering or deciphering of a code.

The outer right-hand armature of relay |4| cooperates with a frontcontact which is connected to ground and the armature is connected byconductor |32 to one terminal of the winding of stepping magnet |25 theother terminal of which is connected to grounded battery. Thus each timethe relay |4| is energized theenergizing circuit of stepping magnet |25will be completed and upon the release of relay |4| stepping magnet |25will be released to effect the advancement of the brushes associatedwith stepping switch banks |25A to |2511', concurrently with theadvancement of the brushes of the stepping switches shown in Figs. 2 and3.

The stepping magnet |3| has one terminal connected to grounded batteryand the other terminal connected to the middle right-hand armature ofrelay |4|. From the front contact with which this armature cooperatesconductor |33 extends through Fig. 1 into Fig. 2 to the front contact ofa relay |34, the armature of which is connected to ground. One terminalof the winding of relay |34 is connected to grounded battery and theother terminal is connected by conductor |66 extending into Fig. 1 toone contact of a normally open pair of contacts |61. Contacts |61 areclosed at the same time as contacts |43 by cam |44. The other contact ofthe contact pair |61 is connected by conductor |68 extending into Fig. 2to one terminal of the lower winding of relay 92, the other terminal ofwhich is connected to the single contact with which the armature of therelay cooperates. The armature of relay 92 is connected by conductor |69extending into Fig. 3 to the front contact associated with an armatureof relay SEER. This armature is connected by conductor to the frontcontact associated with an armature of relay 84ER. This armature isconnected by conductor |12 t0 the front contact associated with anarmature of relay 83ER which is connected to ground.

From the foregoing it will be apparent that when relays 83ER, 84ER andBEER are energized, ground connection will be extended over conductor|69 to the armature of relay 92. If the armature of relay 92 is operatedinto engagement with the right-hand contact, the ground connection willbe extended through the lower winding of relay 92 and over conductor|68, through the contacts |61 when closed and over conductor |66 and thewinding of relay |34 to grounded battery so that relay |34 will beenergized in series with the lower winding of relay 92, which is aholding winding. With relay |34 energized ground connection is extendedover conductor |33 to the middle right-hand front contact of relay |4|which will be energized since when contacts |61 are closed, contacts |43are also closed, and through the middle right-hand armature of relay |4|and the winding of stepping magnet |3| to grounded battery. Whencontacts |43 reopen and relay |4| is released the energizing circuit forstepping magnet 3| is opened and the magnet advances the brushesassociated with the stepping switch banks |3|A le to ISIF to the nextcontacts. The operation of stepping magnet I 3I to effect theadvancement of its associated brushes is thus observed to be dependentupon two factors which do not have cyclic occurrence, namely, theoperation of the armature of relay 92 into engagement with itsright-hand contact and the energization of relays BSER, 3ft-ER and SEER.Other factors also involved which do have cyclic occurrence and areintroduced for timing purposes are the preparation of the energizingcircuit of relay |34 at the cam-operated contacts IST and the completionof theV energizing circuit of relay I 4I at the contacts |43.

The operation of relay 92 to complete the energizing circuit for relay|34 is dependent upon the occurrence of a marking impulse as the secondcode impulse of plain text code signals, by Y which is meant codesignals before being ciphered or after being deciphered, The requirementthat relays 83ER, MER, and BSER be energized in order to extend a groundconnection through to the armature of relay 92 provides that relay |34Shall be energized only in response to some of the occurrences of amarking impulse as the second impulse of text code. The reason for thisis that in a permutation code, one-half of the total number of availablecodes will have the second impulse ofV marking nature so that if thestepping magnet I3I were controlled solely in accordance with theoperation of relay 92 the average frequency of operation of the steppingmagnet would be once for each two codes received or transmitted. It ispreferablethat the stepping magnet I3I shall operate less frequentlythan this since the stepping magnet |25 operates to advance itsassociated brushes once for each code combination received ortransmitted. By supplying the ground connection for operating steppingmagnet II through armatures and front contact of the three relays MER,MER and HER, the average frequency of operation of stepping magnet IBIwill be once for every eight characters received or transmitted.

lIhe operation of relay 92 lwill now be described J and the situationinvolved in the transmission of signals to a distant station will iirstbe considered, this involving signalg generated `by the transmittingcontacts I3. Two facts are to be noted with reference to signaltransmission. One is that the input relay I6 directly follows text codesignals generated by the transmitting contact I3. When a marking signalis generated, relay IE goes to marking in response thereto. The other isthat each time the transmitting contacts I3 are operated to generate asignal contacts 93 are closed and complete the energizing circuit forrelay 9| (Fig. 2), so that its armatures engage their front contacts.Assume that relay I is in marking condition for the second impulse of acode signal and that the relays 8|BR to 853B, are energized incombination to interconnect conductors 44 and MB. The circuit is tracedfrom negative battery on the marking contact of relay |'6 throughconductor S'I to the bridge corner 353, through the branching paths ofthe bridge network rejoining at bridge corner 43 through conductor lili,front contact and outer left-hand armature of relay 9i, conductor 44B,armatures and contacts of certain of the relays BIBR to GEBR, conductor51B, uppermost winding of relay 92V entering at the top of the windingandk leaving at the bottom of the winding, front contact and innerleft-hand armature of relay 9|, conductor 6l, No. 2 code segment andinner ring of distributor 3l, conductor 29, locking winding of relay I5and resistor 26 to ground. The windingsv of relay.92 are polar andWhenthe `circuit is as traced With theupper terminal of the upperIwinding of relay 92 at the marking battery potential and the lowerterminal connected to vthe path to ground, the Awinding is energized inthe direction to drive the armature to the single right-hand contact tocomplete the energizing circuit for relay |34. The circuit includes thelower or locking winding of relay S2 which `becomes energized to .holdthe armature on the right-hand contact. The locking winding of relay 92is subordinate to each ofthe `other three windings so that upon theenergization Vof one of them in the direction to restore the armature toits left-hand position, the locking winding will not prevent suchrestoration. It'merely holds the armature on the .right-'hand contact tohold relay |311 energized until that relay is released bythe opening ofcontacts |67 so that the circuit of stepping magnet ISI will not beinterrupted and the brushes associated therewith stepped until after thetransmission of the last code impulse of a code combination has beeninitiated. Relay 92 preferably has bias Which may be either mechanicalor electrical but which should, however, be subordinated to all of thefour windings shown, including the holding winding, tending to restorethe armature to its left-hand position so that after being operated tothe right-hand position and held there until after the last impulse of acode has been initiated, the armature will be restored to the left-handposition upon the interruption of the holding circuit and Will notremain in the right-hand position until one of the upper three windingsbecomes energized in the direction to drive the armature to itsleft-hand position. Thus the armature of relay 92 will remain in theright-hand position only during the remainder of a cycle of distributor3| in which it was operated to that position due to the occurrence ofthe marking impulse as the second impulse of a text code combination.

If at the time that the relay I6 was operated to marking in response tothe second impulse of the code signal being rgenerated the relaysI SIBRto BR had been energized in such combinations as to connect conductorB'IB to conductor 49B,

"i the circuit would be traced from the armatureof relay I6 through thebranching paths of the bridge network from the bridge corner 38 to thebridge corner 48 and then over conductor 49, the front contact andright-hand armature of relay 9| 'to conductor 49B then to conductor 61Bthrough the armatures and contacts of the second row of cipher codingrelays in Fig. 2 and then to the upper terminal of .the upper winding ofrelay 92 the same as before. It makes no difference whether the circuitfrom the marking contact of relay I6 is completed over conductor 44 orover conductor 49 the Ibattery polarity applied to the upper winding ofrelay 92 will besuch as to drive the armature to the right-handposition. When the second impulse ofthe code generated by transmittingcontact I3 is of spacing nature, the circuits, traced over conductor 44or conductor 49, depending upon the condition of the second row ofcipher coding relays in Fig. 2 will be the same but the polarity appliedto the upper Winding of relay 92 will be reversed, ground beingconnected to the upper terminal of the winding and negative batterybeing connected to the lower terminal of the upper winding through thelocking winding of relay I6. The upper winding of relay 92 will thus beenergized in the opposite direction, tending to drive the armature toitslefthand position to which it has already been operated by itsmechanical or electrical bias.

The operation of relay 92 in response to received signals involves adifferent problem. Relay I6 is not now responding to text code signalsbut is responding to ciphered signals and these signals are decipheredso that the plain text signals appear at relay I1. Accordingly, it isnecessary toI operate the armature o-f relay 92 to its right-handposition when relay I1 is driven to marking for the second impulse of areceived code combination. This is accomplished by the two middlewindings of relay 92.

YWhen signals are being ireceived, contacts 93 are not operated so thatrelay 9| remains deenergized. For an understanding of the operation ofrelay 92 by its two middle windings it is necessary to remember thatwhen the circuit of the operatingl winding of relay I1 is completed fromthe marking contact of relay I6 over conductor 49, the armature of relayI1 goes to spacing, that when the circuit is completed from the spacingcontact of relay I6 over conductor llt the armature of relay I1 goes `tospacing, that when the circuit is completed from the spacing contact ofrelay IS over conductor 49 the armature of relay I1 goes to marking, andthat when the circuit is completed from the marking contact of relay I6over conductor 44 the armature of relay I1 goes to marking.

Taking the first of these four conditions the circuit is traced from themarking contact of relay I6 over conductor 31 to the bridge corner 38,through the two branches of the bridge network r'ejoining at the bridgecorner 49, then over conductor 49 to the lower terminal of the thirdwinding of relay 92 counting from the top, then from the upper terminalof this winding through the back contact and right-hand armature ofrelay 9| to conductor 49B, through armatures and contacts of the secondrow of cipher coding relays of Fig. 2, conductor 51B to the back contactand inner left-hand armature of relay 9| where the circuit of theuppermost winding of relay 92 is now open, conductor 61, No. 2 codesegment and inner ring of distributor 3|, conductor 29, locking windingof relay I6 through resistor 26 to ground. The armature of relay I1 iscaused to go to spacing when the circuit and battery polarity is as thustraced, from which it follows that the second impulse of the decipheredtext code is of spacing nature and the armature of relay 92 should notbe operated to the right-hand position. Accordingly, the third windingof relay 92 is so polarized that with negative battery connected to thelower terminal of that winding and ground connected to the upperterminal the magnetic field produced by the winding tends to drive thearmature to its left-hand position, which position it already occupies.

For the second condition the circuit is traced from ground on thespacing contact of relay I through conductor 31 to the bridge corner 38,then through the branching paths of the bridge network to bridge corner43, then over conductor 44 to the second winding of relay 92 entering atthe right-hand terminal and leaving at the lefthand terminal thereof,through the back contact and outer left-hand armature of relay 9| toconductor 44B, to conductor 61B through armatures and contacts of relays8|BR to 85BR and from this point over the path traced in the precedingparagraph to ground through the locking winding of relay I6 and resistor21 to the negative ter` minal of battery 28, the positive of which isgrounded. The circuit arrangement and battery polarity are such that thearmature of relay |1 is driven to spacing from which it follows that thearmature of relay 92 should not be operated to its right-hand position.Accordingly, it may be stated that with ground on the right-handterminal of the second winding of relay 92 and negative battery on theleft-hand terminal the magnetic field generated is in the directiontending to drive the armature to the left-hand position.

For the third condition the circuit path is identical with thatdescribed for the rst condition but the battery polarity is reversed sothat ground is connected tothe lower terminal of the third winding ofrelay 92 counting from the top and negative battery is connected throughthe locking winding of relay I6 to the upper terminal of the thirdwinding of relay 92. This causes the armature of relay 92 to be drivento the right-hand position which prepares or completes the energizingcircuit for relay |34 as the case may be. The circuit arrangement andbattery polarity is such that the armature of relay |1 is driven to themarking contact.

For the fourth condition the circuit connections are the same as thosedescribed in connection with the second condition but the batterypolarity is reversed, negative battery being connected to the right-handterminal of the second winding of relay 92 and ground being connectedthrough the locking winding of relay I6 to the left-hand terminal of thesecond winding of relay 92. This f causes the armature of relay 92 to bedriven to the right-hand position and the armature of relay I1 to bedriven to the marking contact.

Figs. 5 and 6 show apparatus which in cooperation with the steppingmagnets 8| to 85, |3I and |25 and with the sixth contact bank of each ofthe stepping switches, designated 8 F to 85F, I3 |F and |2'5F, providesfor selectively adjusting the stepping switches shown in Figs. 2 and 3and the left-hand stepping switch in Fig. 4 to any of a plurality ofstarting points and for adjusting the brushes of the stepping switch atthe right of Fig. 4 to the No, 1 contact as a starting point. Referringrst to Fig. 5 a group of seven jacks 20| each having tip, ring andsleeve contacts have those contacts connected to twenty-one of thetwenty-two contacts of stepping switch bank 8IF. These connections maybe made to contacts 1 to 21, inclusive, of the stepping switch bank orthey may be made to contacts 2 to 22. It is of no consequence which oneof the contacts of bank SIF is left unconnected but at all stations itshould be the corresponding contact. Similarly twenty-one of thecontacts of bank 82F are connected to the twenty-one contacts of sevenjacks 202, twentyone contacts of bank 83F are connected to thetwenty-one contacts of seven jacks 203, twentyone of the contacts ofbank 84F are connected to the twenty-one contacts of seven jacks 204,twenty-one of the contacts of bank BEF are connected to the twenty-onecontacts of seven jacks 205 and twenty-one contacts of the steppingswitch bank |3IF (Fig. 4) are connected to the twenty-one contacts ofseven jacks 206 (Fig. 6).

By means of three patching cords, each having three conductors andprovided at both ends with three-circuit plugs, connection may be madefrom any selected three of the jacks 20| to three jacks 2I|. From thering contact of the uppermost jack 2II, from the sleeve contact of themiddle one of jacks 2II and from the tip contact of the lowermost jack21|, individual connections extend to conductors 22|, 222 and 223,respectively, in Fig. 6. In addition, a connection is extended from'thelower or ground terminal of stepping magnet 81 over conductor 21S intoFig. 6. Other sets of three jacks are designated by the referencenumerals 212, 213, 214, 215 and 216. The ring contact of the upper,sleeve contact of the middle, and tip contact of the lower of jacks 212are connected to conductors Y223, 221 and 228, respectively, in Fig. 6.The lower or ground terminal of Stepping magnet 82 is connected toconductor 225 which extends into Fig. 6. Similarly, the ring `contact ofthe uppermost jack 213, the Ysleeve contactrof the middle jack 213 andthe tip contact of the lower jack 2|,3 are connected to conductors 23|,232 and 233, respectively, in Fig. l6. The ground terminal of steppingmagnet 83 is connected to conductor 234 which extends into Fig. 6.

Ten manually operable keys 231 are associated with the conductors 219,22|, 222, 223, 225, 226, 221, 228, 23|, 232, 233 and 234 in Fig. 6. Eachof the keys 231 has three pairs of normally o'pen contacts. Consideringrst the lower pairs of contacts, one contact of each pair is connectedto conductor 219 and the other contact of each pair is connected to oneof the three lconductors 22|, 222 and 223. In the specific arrangementshown in Fig. 6 four of the other contact springs are connected toconductor 22|, three are connected to conductor 222 and three areconnected to `conductor 223. Of the middle pairs of contacts one contactof each pair is connected to conductor 225 and the other contact of eachpair is connected to one of the conductors 226, 221 and 228. Of theupper pairs of contacts, one contact of each pair is connected toconductor 234 and the other contact of each of the pairs is connected toone of the conductors 231,232 and 233.

A second set of ten keys 238 is similarly associated with twelveconductors, nine of which extend from contacts of jacks 21d, 215 and 2|5and the remaining three of which extend from the ground terminals ofstepping magnets 84, 85 and |3|. The connections from the contact pairsof keys 238 to the twelve conductors with which the keys are associatedhave been shown as corresponding to the connections from the contacts ofkeys 231 to the twelve conductors with which they are associated. It isnecessary that the connections be alike only as regards the threeconductors extending from the ground terminals of stepping magnets 84,85 and |31 but as to the connections to the conductors extending fromthe jacks 2|4, 215 and 2|6 the arrangement may be dierent and in actualpractice would probably be different. It should be noted also that therecitation of connections from conductors 22 222, 223, 228, 221, 228,23|, 232 and 233 to specific contacts of jacks 21|, 2l2 and 2|3 issolely by way of example in order to enable circuits to be traced overwhich the keys 231 eiect a control, and that in practice the connectionsbetween any one set of conductors, such as the conductors 22 I 222 and223, and the contacts of the jacks to which they are connected, in thiscase the jacks 21|, may be transposed.

As shown in Fig. 6, a normally open key 24| has one contact connected toground and the other contact connected to one terminal of a relay 242,the other terminal of which is connected to grounded battery. Relay 242has seven armatures all connected to ground and seven .front 24 contactsfrom which conductors 8W, 82V, 83V, 84V, 85V, |3|V `and |25V extendthrough the interrupter contacts of stepping magnets 8|, 82, 33, 84, 85,13| and 125, respectively, to the ground terminals of those magnets.

A relay 8|FR has one terminal connected to the conductor 81V and theother terminal connected to the brush associated with stepping switchbank 3|F. Relays 82FR, 83FR, 84FR, BSFR, |3|FR and |25Fl=|l aresimilarly connected between the conductors 82V, 83V, 84V, 85V, |'3|V and|25V, respectively, and the brushes associated with stepping switchbanks 82F, 83F, 84F, 85F, |31F and |2515?, respectively. Each of theserelays has a single armature and front contact. The front contact ofrelay 8|FR is connected to one terminal of lamp 25|, the other terminalof which is connected to ground. From the armature of relay 8|FR avseries or chain circuit, open at the armature and front contact of eachof the other. relays, extends through to the front contact of relay|25FR which is connected to grounded battery. The last contact instepping switch bank |25F is connected to the ground side of steppingmagnet and no other contact in that bank has any connection.

For the purpose of describing the operation of establishing startingpoints for the stepping switches, several assumptions will be made. Itwill be assumed that patching cords are connected from Athe three jacks21| to theV uppermost three of the jacks 28|, that patching cords areconnected from the jacks 212, to the middle three of the jacks 232,which would be'the third, fourth and fifth of those jacks counting fromthe top and that patching cords are connected from jacks 213 to thelower three jacks of the group 203. Patching cords will also beconnected from the jacks 2|4, 2|5 and 216 to three jacks in each of thesets 264, 205 and 206 but the conductive paths established thereby willnot be Vtraced in detail since the mode of operation will be fullyexempliiied by the description relative Vto the jacks for which specificconnections have been assumed. It will also be assumed that the extremeleft-hand one of the keys 231 is operated, these being locking keys, andthat some one of the keys 238 is operated.

A control circuit may now be traced from the lower or ground terminal ofstepping magnet 8| over conductor 2|8 through the lower pair of contactsof key 231, now closed, conductor 22| t0 the ring contact of theuppermost one of the jacks 21|, through the patching cord assumed to beconnected from the uppermost jack 21| t0 the uppermost jack 28| andthrough the ring contact of the last-mentioned jack to the twentiethcontact of bank 8|F, assuming that the tip contact of the uppermost jack28| is connected to the twenty-rst contact of bank 81F and the sleevecontact of the lowermost one of jacks 20| is connected to the No. 1contact of bank BIF, the other contacts of the jack 28| being connectedin order from bottom to top around the stepping switch bank 8|F in thedirection of rotation of the brush as indicated. Since the brushassociated with stepping switch bank 8 IF is probably not engagingcontact No. 20 at this time, no circuit will be completed over this pathas a direct result of the operation of the Aextreme lefthand key 231.

A second conductive path may be traced from the ground terminal ofstepping switch 82 over conductor 225 through the middle pair of closedcontacts of the left-hand key 231 to conductor 228 which, as previouslystated, is connected to the tip contact of the lowermost jack of group2I2. The path is extended over the patching cord which is connected tothe lifth jack in group 202 and as the tip contact of this jack is theninth jack contact counting from the bottom, it is assumed that the pathextends to the No. 9 contact of stepping switch bank 82E'.

A third conductive path is traced from the ground terminal of steppingswitch 83 over conductor 234 through the uppermost pair of contacts ofthe left-hand key 231 to conductor 233 to which the tip contact of thelowermost jack in group 2I3 is connected. The patching cord extends tothe lowermost jack in group 203 and the path is extended over the tipcontact of this jack to the No. 3 contact of stepping switch bank 83Esince the tip Contact 0f the lowermost jack is the third contactcounting from the bottom.

The particular one of the keys 238 which has been operated completessimilar conductive paths from the ground terminals of stepping magnets86, 85 and I3I to a contact in each of the stepping switch banks 841,85E and ISEF. When one key in each group in Fig. 6 has been operi ated,the advancement of the stepping switch brushes to their start positionsas selectively determined by the particular ones of the keys that areoperated` and by the arrangement of the patching cord is initiated bythe operation of key 24H which completes the energizing circuit forrelay 242, and which must be held while the brushes are being advanced.Ground is applied through the armatures and front contacts of rebrushesare advanced by buzzer operation of their stepping magnets. Assumingthat the brush associated with bank BIF is the first to reach thecontact to which a conductive path has been extended by the left-handkey 231, namely, the

contact No. 20 of that bank, a circuit may be l traced from groundedbattery through the winding of stepping magnet 8l over conductors 2I9,lower contact of the left-hand key 231, conductor 22I, ring contact ofthe uppermost jack of group 2H, patching cord, ring contact of the Y,uppermost jack in group 21H, contact No. 20 and brush of stepping switchbank 8IF, winding of relay SIFR, conductor BI V and front contact andarmature of relay 242 to ground. Over this circuit the winding of relayBIFR is placed in series with the winding of stepping magnet 8| in shuntrelation to the interrupter contacts of stepping magnet 8I so that theenergizing circuit for stepping magnet 8| is not interrupted as a resultof the opening of the interrupter contacts and the brushes controlled bystepping switch 8l remain in engagement with the No. 20 contacts oftheir respective banks. The relay BIFR becoming energized prepares thecircuit of lamp 25|.

As the brush associated with each of the stepping switch banks 82E' toBSF, and I3IF reaches contacts to which a conductive path has been eX-tended by contacts of keys 231 or 238, substitute energizing circuitsfor the stepping magnets are established in shunt relation to theinterrupter contacts and including the relays BZFR to BSFR,

. 26 and I 3IFR so that the stepping switch brushes are arrested and thecircuit of lamp 25| is further prepared for completion. The brushescontrolled by stepping magnet |25 advance until they reach the lastcontact whereupon a substitute energizing circuit for stepping magnet I25 is completed to the last contact and brush of bank l25F' in shuntrelation to the interrupter contacts and including the winding of relayI25FR. which becomes energized. Thus the brushes controlled by steppingswitch I25 are invariably stopped on their last contacts.

The order in which the several sets of stepping switch brushes will bestopped and the relays 8IFR to 85FR, I3IFR and I25FR become energizedwill depend upon the distance the brushes must travel from the randompositions which they occupied before key 24| was closed to the positionsat which they complete substitute energizing circuits for their steppingmagnets. When the last of the relays has been energized the circuit oflamp 25I will be completed and the lamp will be lighted. This serves asan indication that the brushes have reached rest positions asselectively determined by the operated ones of the keys 231 and 238,whereupon key 24| may be released to permit the release of relay 262.Relay 244 upon release removes the ground connections from theenergizing circuits of the stepping magnets and of the lamp controllingrelays so that the magnets and relays release, the magnets advancing thestepping switch brushes one step on the release stroke. This advancesthe stepping switch brushes to the next step beyond the one at whichthey were arrested and in the case of the brushes controlled by steppingmagnet I25F the brushes are brought into engagement with the No. 1contact as the starting point.

From the standpoint of operating routines, the changing of connectionswhere there is provision for such changes may be made once each day,such as upon the starting of the days business in the morning, or morefrequently if it is thought that greater assurance of secrecy is needed.Such changes may involve changing the locations ot plugs such as theplugs SICP, 85DP and 85EP through which connections from the steppingswitch banks to the cipher coding relays are established, substitutionof other plugs for the plugs I I9 and I5I in Fig. 4, and in connectionwith the establishment 0f new starting points for the stepping switches7the rearrangement of the patching cords with reference to the jacksshown in Figs,'5 and 6. New starting points for the stepping switchesmay be established as frequently as is desired under the control of thekeys 231 and 238 and must be established before intercommunication canbe had in cipher between any two stations where a systern involves aplurality of stations of thetype shown in Figs. 1 to 6, inclusive, anytwo of which .may be interconnected through a central switch-

